In order to operate an electronically commutated motor with a low operating voltage, e.g. the battery voltage of a vehicle, at high rotation speed and with good efficiency, e.g. at 10,000 RPM or more, the resistance and inductance of the windings must be very low, and this means that a winding coil should have relatively few turns made of a thick wire, so that the stator slots can be well filled with copper wire.
If stators are automatically wound using so-called “needle winding machines,” it is in many cases not possible to vary the wire gauge of a winding coil, so that one winds multiple wires in parallel.
If one attempts to solve the problem by connecting identical windings in parallel, this results, for a three-phase motor, in four wires, which must be coupled to a terminal (U, V, W) of the stator winding. Thus arises the necessity for time-consuming, expensive manual work.